Alin and paraffin-embedded. Sections (5 mm thick) were stained for insulin, glucagon and microvascular endothelial cells (ECs). For CD34 staining (detection of ECs), antigen retrieval was required (2 min in 10 mmol/l citric acid solution pH 6.0 in a pressurised cooker). Sections were incubated for 1 h at room temperature in either polyclonal guinea pig anti-insulin antibody (1:1000; Dako, Ely, UK) for the detection of b-cells, or with a monoclonal rat anti-CD34 antibody (1:500 AbD serotec, Kidlington, UK) for the detection of ECs. Slides were then incubated for 1 h at room temperature with either a goat biotin anti-guinea pig antibody (1:200; Jackson Immunolaboratories, West Grove, PA, USA) or a rabbit biotinylated anti-rat antibody (1:200; Vector Laboratories, Peterborough, UK). Sections were counterstained with hematoxylin. For immunofluorescence labeling of insulin, a polyclonal guinea pig anti-insulin antibody (1:100; Jackson) was used (1 h at room temperature) with a Texas Red anti-guinea pig secondary antibody (1:40; Jackson; 1 h at room temperature). For immunofluorescence labeling of glucagon, a monoclonal mouse anti-glucagon antibody (1:200; Sigma-Aldrich, Dorset, UK) was used (1 h at room temperature) with a FITC anti-mouse secondary antibody (1:40; Jackson; 1 h at room temperature).Experimental animalsMale C567Bl/6 mice (Charles River, Margate, UK) aged 8?2 weeks were used as donors and recipients. Mice were made diabetic by i.p. streptozotocin (STZ) injection (180 mg/kg; SigmaAldrich, Poole, UK) and those with a non-fasting blood glucose concentration of 20 mmol/l were used as recipients. Blood glucose concentrations were determined using a blood glucose meter and strips (Accu-Chek; Roche, Burgess Hill, UK).Islet isolationIslets were isolated by collagenase digestion (1 mg/ml; type XI; Sigma-Aldrich) followed by density gradient separation (Histopaque-1077; Sigma-Aldrich). After washing with RPMI-1640, islets were picked into groups of 150 for transplantation, as described previously [16].Transplantation of pelleted and manually dispersed isletsThe first experimental series was designed to determine whether manually spreading islets out beneath the kidney capsule was able to maintain normal islet size and morphology. Mice were transplanted with 150 freshly isolated islets either as a single cluster of islet cells that had been centrifuged into pellets (pelleted islets transplant group) in PE50 polyethylene tubing (Becton Dickinson, Sparks, MD, USA) before placing AN 3199 underneath the kidney capsule using a Hamilton syringe (Fisher, Pittsburg, PA, USA). Alternatively, islets were suspended in media and aspirated into PE50 polyethylene tubing and sedimented by gravity. Islets were then spread out over the majority of the upper surface of the kidney capsule, using the Hamilton syringe (manually dispersed islet transplant group).Evaluation of graft morphology and vascular densityFor each animal 5 tissue sections from different regions of the graft were analysed for vascular density. Graft morphology was evaluated by measuring the total purchase 166518-60-1 endocrine area per graft section and extent of islet fusion as previously described [6]. Briefly, to evaluate the extent of fusion between individual islets, the area of individual endocrine aggregates was measured. An individual endocrine aggregate was defined as an area of insulin-positive tissue separated from any other adjacent insulin positive tissue by 50 mm of non-endocrine tissue (insulin-neg.Alin and paraffin-embedded. Sections (5 mm thick) were stained for insulin, glucagon and microvascular endothelial cells (ECs). For CD34 staining (detection of ECs), antigen retrieval was required (2 min in 10 mmol/l citric acid solution pH 6.0 in a pressurised cooker). Sections were incubated for 1 h at room temperature in either polyclonal guinea pig anti-insulin antibody (1:1000; Dako, Ely, UK) for the detection of b-cells, or with a monoclonal rat anti-CD34 antibody (1:500 AbD serotec, Kidlington, UK) for the detection of ECs. Slides were then incubated for 1 h at room temperature with either a goat biotin anti-guinea pig antibody (1:200; Jackson Immunolaboratories, West Grove, PA, USA) or a rabbit biotinylated anti-rat antibody (1:200; Vector Laboratories, Peterborough, UK). Sections were counterstained with hematoxylin. For immunofluorescence labeling of insulin, a polyclonal guinea pig anti-insulin antibody (1:100; Jackson) was used (1 h at room temperature) with a Texas Red anti-guinea pig secondary antibody (1:40; Jackson; 1 h at room temperature). For immunofluorescence labeling of glucagon, a monoclonal mouse anti-glucagon antibody (1:200; Sigma-Aldrich, Dorset, UK) was used (1 h at room temperature) with a FITC anti-mouse secondary antibody (1:40; Jackson; 1 h at room temperature).Experimental animalsMale C567Bl/6 mice (Charles River, Margate, UK) aged 8?2 weeks were used as donors and recipients. Mice were made diabetic by i.p. streptozotocin (STZ) injection (180 mg/kg; SigmaAldrich, Poole, UK) and those with a non-fasting blood glucose concentration of 20 mmol/l were used as recipients. Blood glucose concentrations were determined using a blood glucose meter and strips (Accu-Chek; Roche, Burgess Hill, UK).Islet isolationIslets were isolated by collagenase digestion (1 mg/ml; type XI; Sigma-Aldrich) followed by density gradient separation (Histopaque-1077; Sigma-Aldrich). After washing with RPMI-1640, islets were picked into groups of 150 for transplantation, as described previously [16].Transplantation of pelleted and manually dispersed isletsThe first experimental series was designed to determine whether manually spreading islets out beneath the kidney capsule was able to maintain normal islet size and morphology. Mice were transplanted with 150 freshly isolated islets either as a single cluster of islet cells that had been centrifuged into pellets (pelleted islets transplant group) in PE50 polyethylene tubing (Becton Dickinson, Sparks, MD, USA) before placing underneath the kidney capsule using a Hamilton syringe (Fisher, Pittsburg, PA, USA). Alternatively, islets were suspended in media and aspirated into PE50 polyethylene tubing and sedimented by gravity. Islets were then spread out over the majority of the upper surface of the kidney capsule, using the Hamilton syringe (manually dispersed islet transplant group).Evaluation of graft morphology and vascular densityFor each animal 5 tissue sections from different regions of the graft were analysed for vascular density. Graft morphology was evaluated by measuring the total endocrine area per graft section and extent of islet fusion as previously described [6]. Briefly, to evaluate the extent of fusion between individual islets, the area of individual endocrine aggregates was measured. An individual endocrine aggregate was defined as an area of insulin-positive tissue separated from any other adjacent insulin positive tissue by 50 mm of non-endocrine tissue (insulin-neg.